ORIGINAL ARTICLE The Extended SMAS Facelift Identifying the Lateral Zygomaticus Major Muscle Border Using Bony Anatomic Landmarks Arian Mowlavi, MD, and Bradon J. Wilhelmi, MD n the early 1980s, improving the nasolabial fold promi- Abstract: Extended superficial musculoaponeurotic system (SMAS) rhytidectomy has been advocated for improving nasolabial Inence by elevation of the malar soft tissue ptosis was 1 fold prominence. Extended subSMAS dissection requires release of introduced. Skoog had advocated a superficial musculoapo- the SMAS typically from the upper lateral border of the zygomaticus neurotic system (SMAS) component to the facial skin flap, major muscle and continued dissection medial to this muscle. This thus introducing composite tissue flap elevation to rhytidec- maneuver releases the zygomatic retaining ligaments and achieves tomy. Additionally, a biplanar face lift technique had been more effective mobilization and elevation of the ptotic malar soft developed, utilizing independent SMAS and cutaneous flaps.2 tissues, resulting in more dramatic effacement of the nasolabial This technique intended to allow more aggressive traction of crease. Despite its presumed advantages, few reports have suggested central facial tissue by the SMAS but without the resulting greater risk of nerve injury with this technique compared with other “pulled” effect typically observed on the overlying skin. limited sub-SMAS dissection techniques. Although the caudal ex- tent of the zygomaticus muscle insertion to the modiolus of the Next, skin flaps were extended medially across to the naso- mouth has been well delineated, the more cephalad origin has been labial fold in an attempt to increase effacement of the naso- 3 vaguely defined. We attempted to define anatomic landmarks which labial crease. Despite these maneuvers, nasolabial fullness could serve to more reliably identify the upper extent of the lateral was observed to persist or recur prematurely. Finally, modi- zygomaticus major muscle border and more safely guide extended fications to the biplanar technique, such as the extended sub-SMAS dissections. Bilateral zygomaticus major muscles were SMAS technique, evolved following delineation of the me- identified in 13 cadaver heads with 4.0-power loupe magnification. dial SMAS anatomy.4 Bony anatomic landmarks were identified that would predict the Several anatomic studies followed Skoog’s initial in- location of the lateral border of the zygomaticus major muscle. The troduction of the SMAS and its suspension within the skin upper extent of the lateral border of the zygomaticus major muscle flap.1 Mitz and Peyronie5 provided the first detailed anatomic was defined in relation to an oblique line extending from the mental 4 protuberance to the notch defined at the most anterior-inferior aspect studies of this fascial layer. Nearly a decade later, Wasef of the temporal fossa at the junction of the frontal process and reaffirmed the medial attachment of the SMAS to the zygo- 6 temporal process of the zygomatic bone. The lateral border of the maticus major muscle. Finally, Barton differentiated the zygomaticus major muscle was observed 4.4 Ϯ 2.2 mm lateral and superficial and deep SMAS layers surrounding the zygomat- parallel to this line. More accurate prediction of the location of the icus major muscle and discussed its implications. Since the upper extent of the lateral border of the zygomaticus major muscle SMAS fascia surrounded the zygomaticus major muscle, using the above bony anatomic landmarks may limit nerve injury lateral pull on the SMAS produced limited excursion of the during SMAS dissections in extended SMAS rhytidectomy. soft tissue overlying the central face. This limitation was due (Ann Plast Surg 2004;52: 353–357) to zygomaticus major muscle’s underlying deep tissue attach- ments, especially at its unyielding cephalad origin.6 In fact, several clinicians argued that lateral traction on the SMAS Received June 9, 2003 and accepted for publication August 22, 2003. would be transmitted to a pull on the zygomaticus major From the Plastic Surgery Institute, Southern Illinois University, School of Medicine, Springfield, IL. muscle, and paradoxically, only serve to deepen the nasola- 3 Reprints: Bradon J. Wilhelmi, MD, Assistant Professor, The Plastic Surgery bial fold. Extended SMAS techniques developed following Institute, Southern Illinois University, School of Medicine, 747 N. anatomic delineations of the medial SMAS extension as well Rutledge, P.O. Box 19653, Springfield, IL 62794–9653. E-mail: as the nasolabial fold and crease.7,8 [email protected] Copyright © 2004 by Lippincott Williams & Wilkins In 1987, Millard attributed the prominence of nasola- ISSN: 0148-7043/04/5204-0353 bial crease to its adjacent lateral fullness due to accumulation DOI: 10.1097/01.sap.0000099712.80882.6b of subcutaneous fat.9 This accumulation of subcutaneous fat Annals of Plastic Surgery • Volume 52, Number 4, April 2004 353 Mowlavi and Wilhelmi Annals of Plastic Surgery • Volume 52, Number 4, April 2004 pad was subsequently recognized as descent of the malar fat more reliably identify the upper extent of the lateral zygo- pad from its original position overlying the zygomatic but- maticus border and more safely guide extended SMAS dis- tress.10 In summary, the nasolabial crease gained prominence sections. as a result of nasolabial fold accumulation of ptotic malar fat pad. The malar fat pad was described as a triangular area of MATERIALS AND METHODS bulky subcutaneous fat overlying the maxillary zygomatic Thirteen cadaver heads were dissected using a standard region with its base at the nasolabial fold and its apex at the rhytidectomy skin incision and skin and/or SMAS flaps infraorbital fibers of the orbicularis oculi muscles.11 The elevated medially until the junction of the SMAS and zygo- SMAS-mimetic muscle layer was described as maintaining maticus major lateral border was identified. Bony anatomic dermal attachments to the nasolabial crease, which rendered landmarks were identified that were easily palpable and that it more prominent with muscle animation such as smiling.12 would predict the location of the lateral border of the zygo- Moreover, Mendelson demonstrated zygomaticus major mus- maticus major muscle. The lateral border of the zygomaticus cle fiber insertions medial to the nasolabial crease at the major muscle was defined with respect to the bony landmarks modiolus. Thus, simple lateral traction of the SMAS was using 4.0 loupe magnification and surgical calipers. (Fig. 1 discouraged since it was felt to exaggerate the nasolabial fold and 2) by pulling the nasolabial crease beneath the fold.13 This conclusion was further substantiated by the fact that the RESULTS nasolabial fold disappeared in cases of facial paralysis.12 The zygomaticus major muscle was present in all ca- During the latter part of the 1980s and the early 1990s, daver heads examined. The upper extent of the lateral border several clinicians advocated more extensive dissection of the of the zygomaticus major muscle was defined in relation to an SMAS medial to the zygomaticus major muscle to gain more oblique line extending from the mental protuberance to the controlled traction on the central facial area and more effec- tive effacement of the nasolabial crease.13–17 However, the benefits observed on nasolabial crease effacement needed to be weighed against its complications. Specifically, various modifications of the extended SMAS were reported to be associated with increased risk of transient facial nerve pare- sis. Mendelson13 reported several cases of transient mild weakness with closure of the eyelid on blinking, as well as weakness of the upper lip; included in this retrospective report of 135 cases were 3 prolonged cases of paresis. Barton14 reported a single case of transient upper lip weak- ness in his retrospective review of 100 cases. Hamra15 de- scribed 2 cases of upper lip weakness which resolved after 3 weeks in his retrospective review of 403 cases. Finally, Owsley17 reported that few patients demonstrated temporary mild decreased levator function characterized by restricted lip elevation which cleared over 2 to 3 weeks; he attributed these symptoms to increased swelling in his retrospective review of 400 cases. All of the described extended SMAS techniques require release of the SMAS fibers spanning the upper lateral border of the zygomaticus major muscle, followed by continued dissection medial to this muscle. This release and subsequent medial dissection, unique to extended SMAS rhytidectomy, may be associated with increased risk of facial nerve injuries. FIGURE 1. In an attempt to minimize the increased risk of injury to the The upper extent of the lateral border of the zygomaticus major muscle was defined in relation to an facial nerve, the upper lateral border of the zygomaticus oblique line extending from the mental protuberance to the major was defined using bony anatomic landmarks. Although notch defined at the most anterior-inferior aspect of the tem- the caudal extent of the zygomaticus muscle insertion to the poral fossa at the junction of the frontal process and temporal modiolus of the mouth has been well delineated, the origin process of the zygomatic bone. The lateral border of the 18 and more cephalad extent has been vaguely defined. We zygomaticus major muscle was observed on average 4.4 Ϯ 2.2 attempted to define anatomic landmarks which could serve to mm lateral and parallel to this line. 354 © 2004 Lippincott Williams & Wilkins Annals of Plastic Surgery